Buggy code:
public class LineRangeOperationCommand extends CountIgnoringNonRepeatableCommand { private static final String START_SEL_RE = "^\\s*(%|\\$|[+-.]?\\d+|\\.|\\^|\'[<\\[a-zA-Z]|([?\\//])((?:\\\\2|.)+?)\\2)([+-]\\d+)?\\s*" ; private static final String END_SEL_RE = "\\s*[,;]\\s*([+-.]?\\d+|\\.|\\$|\'[>\\]a-zA-Z]|([?\\//])((?:\\\\6|.)+?)\\6)([+-]\\d+)?\\s*" ; private static final Pattern START_AND_STOP = Pattern . compile ( ( ( ( LineRangeOperationCommand . START_SEL_RE ) + ( LineRangeOperationCommand . END_SEL_RE ) ) + "(\\D.*)" ) ) ; private static final Pattern JUST_START = Pattern . compile ( ( ( LineRangeOperationCommand . START_SEL_RE ) + "(\\D.*)" ) ) ; private static final Pattern JUST_STOP = Pattern . compile ( ( ( "^" + ( LineRangeOperationCommand . END_SEL_RE ) ) + "(\\D.*)" ) ) ; private static final Pattern COPY_MOVE = Pattern . compile ( "^(t|co(p(y)?)?|m(o(v(e?)?)?)?)\\s+.*" ) ; private String definition ; private String startStr = "" ; private String stopStr = "" ; private String operationStr = "" ; public LineRangeOperationCommand ( String definition ) { } public static boolean isLineRangeOperation ( String command ) { } public static boolean isCurrentLineCopyMove ( String command ) { } public String getOperationStr ( ) { } public void execute ( EditorAdaptor editorAdaptor ) throws CommandExecutionException { } private void parseRangeDefinition ( ) { } public Selection parseRangeDefinition ( EditorAdaptor editorAdaptor , boolean linewise ) { } public SimpleTextOperation parseRangeOperation ( EditorAdaptor editorAdaptor ) { if ( operationStr . isEmpty ( ) ) { editorAdaptor . getUserInterfaceService ( ) . setErrorMessage ( "No<seq2seq4repair_space>operation<seq2seq4repair_space>specified." ) ; return null ; } while ( operationStr . startsWith ( ":" ) ) { operationStr = operationStr . substring ( 1 ) ; } char operation = operationStr . charAt ( 0 ) ; if ( operation == 'y' ) { if ( ( ( operationStr . length ( ) ) > 2 ) && ( ( operationStr . indexOf ( '<seq2seq4repair_space>' ) ) == ( ( operationStr . length ( ) ) - 2 ) ) ) { return new YankOperation ( operationStr . substring ( ( ( operationStr . length ( ) ) - 1 ) ) ) ; } else { <START_BUG> return YankOperation . INSTANCE ; <END_BUG> } } else if ( operation == 'd' ) { return DeleteOperation . INSTANCE ; } else if ( ( operation == 's' ) && ( operationStr . startsWith ( "sort" ) ) ) { return new SortOperation ( operationStr . substring ( 4 ) ) ; } else if ( operation == 's' ) { return new SubstitutionOperation ( operationStr ) ; } else if ( ( operation == 'g' ) || ( operation == 'v' ) ) { return new ExCommandOperation ( operationStr ) ; } else if ( ( operation == 'r' ) && ( operationStr . startsWith ( "ret" ) ) ) { return new RetabOperation ( operationStr ) ; } else if ( ( operation == 'c' ) || ( operation == 't' ) ) { return new CopyMoveLinesOperation ( operationStr , false ) ; } else if ( operation == 'm' ) { return new CopyMoveLinesOperation ( operationStr , true ) ; } else if ( operation == '!' ) { return new PipeExternalOperation ( operationStr ) ; } else if ( ReadExternalOperation . isValid ( editorAdaptor , operationStr ) ) { return new ReadExternalOperation ( operationStr ) ; } else { editorAdaptor . getUserInterfaceService ( ) . setErrorMessage ( ( "Unknown<seq2seq4repair_space>operation<seq2seq4repair_space>for<seq2seq4repair_space>range:<seq2seq4repair_space>" + ( operationStr ) ) ) ; return null ; } } }

Fix:
return new YankOperation ( null , false ) ;